This invention relates to vacuum pumps and, more particularly, to a motor driven compressor assembly including a motor that is fluidly connected to a compressor.
Typical motor driven compressor assemblies include a reluctance motor fluidly connected to an inlet port of a screw compressor such that the operation of the screw compressor evacuates an internal portion of the reluctance motor. The reluctance motor includes a rotor that rotates relative to a stator. The rotor is spaced apart from the stator such that air evacuated from the reluctance motor passes through the space between the rotor and the stator. The compressor thereby produces a low pressure within the internal portion of the reluctance motor. The rotor produces less noise with lower air pressure, however, the low pressure may produce a pressure drop at the inlet port of the compressor. As a result of the pressure drop, the compressor may operate inefficiently or produce an inconsistent vacuum.
Another problem with typical motor driven compressor assemblies is that the reluctance motor produces significant heat during operation. If the heat is not adequately removed, the reluctance motor may overheat which may result in a malfunction in the reluctance motor or the compressor.
Conventional motor driven compressors utilize air flow through the space between the rotor and the stator to communicate heat away from the reluctance motor. Disadvantageously, the space is too small to flow a significant quantity of air there through, which minimizes heat dissipation from the reluctance motor.
Accordingly, there is a need for a motor driven compressor assembly that more effectively cools the motor without a significant pressure drop at the inlet of the compressor.